Emission standards for unburned hydrocarbons, carbon monoxide and nitrogen oxide contaminants continue to become more stringent. In order to meet such standards, catalytic converters containing a three-way conversion (TWC) catalyst are located in the exhaust gas line of internal combustion engines. Such catalysts promote the oxidation by oxygen in the exhaust gas stream of unburned hydrocarbons and carbon monoxide as well as the reduction of nitrogen oxides to nitrogen. Government regulations (such as LEVIII in the US and Euro 6 & 7 in Europe) are targeting emissions during cold start and before the catalyst has fully warmed up. One strategy to address this is to ensure platinum group metals (PGMs) are delivered by supports that do not interfere with and that enhance performance of PGMs at lower temperatures.
A catalyst with lanthanide-doped zirconia as a support for TWC applications is presented in U.S. Patent Appln. Pub. No. 2013/0115144. WO9205861 discusses a co-formed ceria-zirconia composite to be used to support rhodium where a base metal oxide may be co-dispersed onto the support with the rhodium as a promoter.
There is a continuing need in the art to provide catalytic articles that provide excellent catalytic activity and/or light-off performance and/or efficient use of components to achieve regulated emissions.